Engine starter drive



April 21, 1953 w, LEWls 2,635,471

ENGINE STARTER DRIVE Filed June 27, 1950 INVEN TOR. George I44 Lew/s Patented Apr. 21, 1953 UNITED STATES PATENT OFFICZE 18 Claims.

The present invention relates to engine starters and more particularly to a starter drive of the yielding and automatic engine meshing and demeshing type.

The invention contemplates a starter drive incorporating novel means arranged to cause the meshing engagement of the starter pinion with the engine gear upon a small initial rotation of the starting motor whereby only a very small amount of kinetic energy is stored in the rotating parts, thus reducing the shocks and stresses produced by the meshing and sudden application of the kinetic energy of rotation and deceleration torque of the starting motor to the engine gear.

The invention comprises a small and compact starter drive of very simple construction and assembly adapted to maintain operative connection with the engine gear until the engine is reliably self-operative.

The invention comprehends a starter drive including a novel arrangement of novel inertia means operable to cause the starter pinion to traverse readily into mesh upon the initial rotation of the power shaft but which resists reverse traverse when the pinion and associated parts are rapidly rotated, thus preventing rebounds.

The invention embraces a starter drive incorporating fully enclosed threaded members loosely coupled to decrease friction therebetween enhancing meshing with the engine, but in which all of the parts of the drive are so mounted and piloted with respect to the power shaft that concentric relationship and proper alignment are always maintained.

According to the foregoing summary of the invention indicating its general nature and substance, its main objective is to provide a starter drive for engines wherein the meshing operation is instantaneously obtained and cranking is maintained until the engine is reliably self-operative, preventing pinion rebounds after demeshing.

In prior known starter drives of the automatic engine meshin and demeshing type, the longitudinal movement of the pinion is secured after the motor has attained considerable velocity and speed due to the friction of the pinion assembly on the shaft and that of the threaded connection which provides the longitudinal movement of the pinion. Hence, friction of the pinion assembly in its longitudinal movement relatively prolongs the free-running period of the motor. Prolongation of the free-running period of the starter motor, or permitting such period to be of considerable duration, produces a very high kinetic energy or rotation of the motor armature and parts rotated thereby. so that shock and. stresses at the initial starting, due to'the deceleration torque and the torque of the motor, are of very high magnitude, causing chopping of the ring gear teeth as well as those of the pinion. Thus the effective operation of the starter drive, as well as the life of the engine flywheel gear, is materially impaired, causing performance failures after comparatively short periods of use.

The starter drive of the invention overcomes the listed drawbacks and performance failures by reducing the friction of the threaded connection as well as that of the pinion assembly, and by the use of novel inertia means for accelerating the meshing operation and initiating the application of torque for cranking the engine before the motor attains considerable velocity and speed. Thus the free-running period of the starter motor is of very short duration whereby the deceleration torque and kinetic energy of rotation of the armature and parts rotated therewith is maintained at exceedingly low value.

The invention includes as one of its objects a novel engine starter drive incorporating threaded members, loosely coupled, to decrease the friction therebetween so as to eliminate the possibility of binding and insuring, at all times, acceleration in the meshing operation of the pinion with the engine gear, particularly in cold weather.

Another object of the invention is to provide a novel starter drive incorporating interconnected members having a non-symmetrical threaded connection of special and improved configuration to thereby maintain the pinion in engagement with the engine gear until the engine is reliably self-operative.

Another object of the invention is the provision of a compact starter drive which includes a freely rotatable eccentric inertial mass, frictionally journaled on the pinion assembly, whereby upon rotation of the power shaft, meshing of the pinion with the engine flywheel gear is instantaneously obtained, so that the free-running period of the starting motor is of a very short duration whereby the deceleration torque and kinetic energy of the motor is maintained at exceedingly low values.

Another object of the invention is the provision of a very quiet starter drive in which the pinion supports a freely rotatable eccentric inertial mass urged against its teeth by a spring, the arrangement being such that on the demeshing operation, the inertial mass acquires high velocity and the energy stored thereby is frictionally dissipated against the pinion and actuating elements, thus preventing the starter pinion from rebounding toward the engine member.

Another object of the invention is to provide a very quiet starter drive wherein the parts fixed to and operated by the armature during the free-running period of the motor have very low turning moment and are of very low kinetic energy of rotation whereby the meshing shock and stresses are materially minimized.

Another object of the invention is the provision of a connection having inclined splines or threads of asymmetrical cross-section, so arranged that thread-clutching action is minimized in one side to prevent the sticking of the pinion in idle position when thrown back by the starting of the engine and where threadclutching action is discreetly cultivated on the pressure side to prevent premature demeshing of the pinion.

A further object of the invention is the provision of a novel starter drive which is dimensionally small without sacrificing sturdiness and long life and which includes a rotatable eccentric inertial mass, frictionally connected to the pinion, which, upon rotation of the power shaft, accelerates the longitudinal movement of the pinion and which, during the cranking of the engine, produces a radial force which imposes a resistance to the endwise movement of the pinion, reducing thereby pumping and the backout of mesh of the pinion during the engine cranking operation.

A further object of the invention is to provide a unitary starter drive embodying simple provisions for insuring the meshing of the pinion with the engine gear in case of end-to-end abutment between the teeth of the pinion and the engine gear.

A further object of the invention is the provision of a starter drive wherein the component interengaging, relatively movable parts are enclosed, protecting their contacting surfaces against water, dirt, and foreign substances.

Other objects and advantages of this invention relating to the arrangement, operation and function of the related elements of the structure, to various details of construction, to combinations of parts and to economies of manufacture, will be apparent to those skilled in the art upon consideration of the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Referring to the drawings:

Fig. I is a side elevation, partially in section, showing a form of the invention with the parts in idle position;

Fig. II is a view similar to Fig. I showing the parts thereof in engine cranking or operating position;

Fig. III is an enlarged fragmentary sectional view of the threaded connection of the invention;

Fig. IV is a front View of the drive taken along the line IV--IV of Fig. I;

Fig. V is a sectional view taken along the line V-V of Fig. I, looking in the direction of the arrows.

The invention may be incorporated in any type of engine starting apparatus and for a practical application of its principles, the invention is shown in the drawings as embodied in an electric starter for internal combustion engines. However, it is to be understood that the invention is not limited to the particular form shown but that it is contemplated to use the same with any suitable prime mover and whenever the invention or its components may be found to be of utility.

Referring to the drawings, in the embodiment illustrated, the prime mover is shown in the form of an electric motor I0 preferably of the series type. The motor I0 operates the power shaft which is shown as an extended armature shaft I2 journaled on a suitable bearing I3 carried by the flanged end plate I4 by means of which the motor and the drive of the invention are attached to the engine block not shown. As illustrated in Fig. I, the starter drive is a self-contained unit having an outer housing or barrel I5 fixed to the power shaft I2 by suitable means. A key I6 and a set screw I! carried by the hub or collar I8 of the barrel I5 rigidly secures the starter drive as a unit on the shaft I2 locating the engine driving member or pinion 20 in a position to be automatically moved into and out of meshing engagement with a member of the engine to be started such as a flywheel ring gear 2I.

The novel means of the invention to effect the automatic engagement of the starter drive with the engine to be started upon initial rotation of the starter motor I0 includes a concentrically supported, loosely coupled, inclined, torquetransmitting connection of reduced area of engagement, providing a longitudinal component to the pinion. The inclined connection is interposed between a member journaled on the power shaft or pinion actuator 23 connected to the pinion hub or sleeve 24 and a driving head or control member 25 mounted on the barrel I5 in concentric relation with the power shaft I2. In the preferred embodiment this connection takes the form of helical splines or screw threads having a liberal clearance between their sides as well as between their major and minor diameters throughout their entire length to decrease the area of contact and friction therebetween, reducing thereby the resistance to the longitudinal movement of the pinion 20 toward the engine member 2 I.

The torque-transmitting connection of the invention, as shown in Fig. I, comprises male type screw threads 26 of non-symmetrical sides 21 and 28 formed on the outer cylindrical surface of the pinion actuator 23 for cooperative engagement with internal screw threads 29 having corresponding non-symmetrical sides 30 and 3I formed on the bore of the control member or driving nut 25. The threads 26 and 29 are preferably of the triple screw type, being formed and correlated to provide generous spacing between their sides and a liberal thread-crest-clearance or spacing between their major and minor diameters over conventional maximum tolerances. The liberal thread-crest-clearance, which reduces the area of engagement of threads 26 and 29, is always maintained by mounting the actuator 23 and nut 25 in concentric relation upon shaft I2. Thus, a loosely coupled helical connection of reduced area is provided to enhance the meshing operation and which is very advantageous in eliminating sticking of the pinion under dirty or oily cold starting conditions.

The sleeve section 24 of the pinion 20 is counter-bored as at 32, reducing its bearing area on the shaft I2 and has its outer end telescopicly splined to the actuator 23 which is directly journaled on shaft I2. To reduce friction of the actuator 23 on shaft I2, and insure concentric relation of the loosely-coupled connection 26-29, the bore 34 of the actuator 23 is provided with four bearing segments or lugs 35 of narrow radial width formed to directly engage shaft l2. The right angle positioned lugs 35 have a sliding fit onthe longitudinal slots 36 formed at the end of the pinion sleeve 24 which. in turn, snugly fit the bore 34 of the actuator, the slots being closed by a snap ring 31. Thus the pinion and its actuator have a telescopic splined connection which provides positive rotary motion together and a limited longitudinal lost motion therebetween. i

In order to complete the traverse and torquetransmitting connection between the power shaft l2 and the pinion and maintain the concentricity of the threaded connection 26-29 with the axis of rotation of the drive, the driving head is connected and piloted on the barrel IS. The driving head 25 is connected to the barrel l5 for positive rotary movement together but having relative longitudinal sliding movement by four radial equidistant members such as the rightangle-positioning set of tongues 38, 39, having a sliding fit in the longitudinal open slots formed at the front end of the barrel l5. The four equidistant slots 40 also accommodate the radial lugs of the thrust washer or stop 4| and are closed by the snap ring 42 fitting into the barrel groove 43, limiting thereby the outward movement of the stop 4| and driving nut 25. The two sets of right angle-positioned tongues 38, 39, through the sliding fit with each of the four equidistant slots 40, insure at all times the liberal threadcrest-clearance and the concentricity of the internal threads 29 carried by the driving head 25 with respect to the threads 26 carried by the actuator 23 journaled on the shaft l2, so that their reduced contacting area is always maintained.

In the embodiment shown, a compression member or coil spring 45, interposed between the driving nut or control head 25 and the barrel rear wall or shoulder 46, provides the yielding means for cushioning or taking up the shock of meshing engagement of the drive and for building up torque for the gradual application by the pinion to the engine ring gear for starting theengine. The spring 45 is assembled under an initial preload, so that the same functions to urge the control head 25 in abutting engagement with the thrust washer or stop 4|. It is contemplated that other suitable yielding means that perform the functions indicated may be substituted for the coil spring 45 such as a distortable mass which may take the form of a compressible rubber sleeve.

The means provided for normally holding the driving member or pinion 20 and its control member or driving screw 23 in extended position in their interlocking longitudinal lost motion connectionjpermitting, in case of tooth abutment of pinion and engine ring gear teeth, a yielding backward movement of the pinion, are shown in the form of a resilient member such as a coiled spring 41 surrounding the sleeve section 24 of the pinion. The spring 41 is assembled under an initial preload by being interposed between the'forward end of the driving screw 23 and rear surface of the rotatable eccentric inertial mass of the invention which thereby-urges into frictional engagement its front surface with the non-working ends 52 of the chamfered teeth 53' of the pinion 20. This arrangement provides a very simple longitudinal yielding connection to effect the meshing of the pinion 20 and flywheel ring gear 2| in case the chamfered teeth 53 of I the pinion and those of'the engine ring gear meet end to end during the shifting opera tion. V

"one of the important features of the invention is manifested by the provision and arrangementof a freely rotatable and slidable eccentric inertialmass, frictionally journaled and resiliently slidable on the pinion assembly which functions inv a three-fold manner: First, as means to accelerate the meshing of the pinion with the engine gear upon initial rotation of the motorshaft; second, as means which produce a radial force imposing resistance to the endwise movement of the pinion, reducing thereby pumping and backout of mesh of the pinion during the cranking operation; and, third, as means to synchronize the pinion with the armature shaft to resist pinion rebounds on the demeshing operation.

The rotatable inertial mass of the invention may take the form of a weight member having its major mass or weight arranged at one side of its axis of rotation to overbalance the same. In the embodiment shown, the inertial member takes the form of a disc-like or separable counterweight 56 which is provided with an opening 5| located at a point oifset from its center of mass, by means of which the counter weight is mounted on the outer surface of the pinion sleeve 24. The member 56 is frictionally journaled and resiliently slidable on the pinion sleeve by having its front surface '54 in frictional engagement with the non-working ends 52 of the pinion teeth 53 by a coil spring 47. The coil spring, as herein-. before described, is assembled with an initial preload between the driving screw 23 and the rear surface 55 of the inertial mass 5|]. The coaction and cooperative relationships by which the frictionally journaled and resiliently slidable eccenis shown in the form of a light compression or coiled spring 58 surrounding the motor or power shaft l2. The anti-creeping spring 58 is arranged to bear at one end against the outer surface of the power shaft bearing l3 and at its other end against the pinion 20. This arrangement provides sufficient frictional resistance to prevent the possibility of rotary movement of the pinion 26 on the power shaft |2 due to vibration. Thus not only holds pinion 29 in its home or retracted position, but aids in the shifting of the pinion the instant the power shaft I2 rotates.

Another important feature of the invention resides in imparting different angularity to the best shown in Fig. III, these objectives can be secured by forming both non-pressure sides 21' and 3| of the threads 26 and 29 substantially perpendicular to the axis of rotation of the shaft or having a small angle A with the vertical which may vary from 0 to 15' degrees, while both pressure sides 28 and 30 of the threads are inclined forming a larger angle B with the ver-' tical ranging between 30 to 50 degrees.

"I" have found that. the invention can be.

eiiectiveiy carried into practice by ionizing, t e incline or. pressure side respectively of the threaded connection 2629 at an angl of approximately 30. degrees with the vertical, while the. nonrpressu-reor vertical side 21- and 3| esp ctively of. s id connection is. formed at an angle. of, 5, degrees with the vertical, so that the overall. angle between the. sides of each thread is .35 degrees. However, it is understood that the objectives of. the invention are realized. by the,

angularity specified for the pressure and nonpressure. sides of the threaded connectionas. the thread-clutching action for each side is, properly controlled.

It should be noted that by forming the. inclined or pressure side of both threads at an angle ranging between .30 to 50 degrees from pianw perpendicular to. the axis. of rotation, the thread-clutching action of the threaded conne tion of reduced area of the invention is discreetly cultivated to prevent objectionable pumping of the pinion over the engine compression points or when torque fluctuations take place, as. well as disengagement or premature demeshing of the, pinion in the case of a false start. By a false start is meant one in which one of the cylinders, of the engine fires or the engine attempts to become self-operative but fails and stops. Inv addition, the thread-clutching action of'th inclined or pressure side of the threads coacts with the eccentric rotatable inertial mass 5.6 to maintain the pinion 20 in mesh with the engine ring gear 2| until the engine is reliably self-operative. By forming the non-pressure side of each of the threads almost vertical or at an angle ranging between to 15 degrees from the vertical, their thread-clutching action is minimized to prevent sticking or binding of the pinion in its idle position when the same is propelled or thrown back by the starting of the engine.

The foregoing functional advantages obtained by the use of splines or threads of non-symmetrical sides for the threaded connections 26-48 are materially enhanced due to the reduced friction and limited area of contacting en.- gagement of the screw threads 26 and 29. This reduced friction and limited area is obtained by the liberal thread-crestclearance which may takethe form of a 72 space between the major and minor thread diameters, as well as by the fact that while the threads are formed and correlated to provide a generous longitudinal space ing therebetween, there is at all times fulltconcentricity and a. complete coincidence between the axis of rotation of the power shaft 12 with that of the male and female screw threads, 26 and 29.

The operation of the engine starter .of the invention may be summarized as follows: start.- ing the cycle of operation with the parts in the position shown in Fig. I, rotation of the power shaft. I! by the energization of the motor 1!! is transmitted through barrel l5 and driving head 25. by the loosely-coupled threaded connection 26-29 to the control member 23 and thereby to the pinion 20. Upon the initial rotation of the power shaft [2, the rotation of the pinion 20. is

substantially prevented or checked owing to its.

inertia. and that of the rotatable :eceentrically mounted, weighted member 50. which alsoyimposes frictional. resistance to the turning or the pinion in addition to. that of the antiecreemng spring 5.8. The coaction of the rotatab e eccentric weight .50 with the pinion assembly ren ders immediately efi'eotive the longitudinal component oi the. torque-transmitting connecti n 26.29 to accelerate the meshing of the pinion 2| with the engine ring gear 21 upon the initial rotation of thepower shaft, 12. Due to the limited area of contact to the pinion assembly with the power shaft, as well as the reduced area of contacting engagement of the threads 25 and 28. the pinion 2,0. is p p led into e ga men with the ring gear 2| before the power shaft I: attainsconsiderable. velocity and speed.

In ase orinterference wi h the propulsion o! the. pinion 20 to its. en ine-mesh n pos ti n. such as. tooth abutm nt. with the ring sear teeth. the driven screw 23 will continue to move axially and. the. thrust is. absorbed by the spring 41 through the lost motion connection between the pinion 20 and screw member 23. Such interfering action initiates the transmission of torque from the driving head 25 to the pinion 2.0. turning it to bring its. chamfered teeth 53 into registration with those of the enginev lear- 2I. Consequently, the, expansive force. of the. spring 4] quickly meshes the pinion 20 with. the engine ring ear. 2|.

The full meshing enga ement of the. pinion 20 with the engine ring gear 2!, as shown in II, is defined by the abutting eng ement of thev control screw 23 with the stop or thrust washer 4| carried by the barrel I5. This engagement. will stop further longitudinal movement. or the pinion 20 toward the. engine gear 2|. and initiate the. gradual transmission. of torque to the pinion to crank the engine. The load of turning the engine will be manifested by a longitudinal component in the reverse direction caused by-the screw jack action of the concentric looselycoupled threaded connection 26-48 causing the driving head 25 to move rearwardly to com:- press the spring 45. Thus the turm'ng force to crank the engine is transmitted from the starting motor to the pinion in a yielding manner by the compression of the spring 45 caused by the axial movement of the head 25 with respect'to the barrel l5 permitted-by its piloting connection with the barrel which provides a longitudinal. movement therebetween.

During the engine cranking operatiomthe inertial mass 50 rotates with the pinionlfl and the frictional contact of the bore of the inertial mass with the sleeve of. the pinion is added to the frictional contact of the inertial mass with the nonworking side 52 of the pinion teeth 53 caused by the spring member 41. Moreover, due to the fact that the inertial mass 50 has its center of mass displaced from the center of rotation. the radial force developed by centrifugal action lm. poses a radial. load. on the pinion which is proportional to the squareof the velocity of the inertial mass. The combined action of the frictional resistance, due to the plural contacting surfaces of the inertialmass with the pinion. and the-radial load imposed on thepinion by. the inertial mass, operate as means to check relative rotation between the pinion. and inertial mass. Therefore, any change inthe speed of the engine member is resisted by the kinetic energy oi rotation or the rotational inertia of the. inertial mass 50. Moreover, the cumulative eflect of the frictional resistance, radial .load.. and rotational inertia of the inertial. mass operate, whenthe engineoverruns the speed of the pinion .or fluetuations cf the torque transmitted takes Place. to check the screwjackaction oi threaded connection 2629, opposing thereby premature dc,- meshing or axial movement of the pinion with respect to the engine ring gear. the rotatable inertial mass 50 with the discreet respect to the engine flywheel, thus counter-acting any pumping action of the pinion with The coaction of of these sides and the interaction therewith of the eccentric rotatable weight 50 provides an eifective arrangement to maintain the pinion in mesh until the engine is reliably self-operative.

When the engine starts under its own power, the acceleration of the ring gear 2% revolves the pinion at a higher speed than the motor shaft l2 and thereby the pinion 28 will be screwed out of meshing engagement with the ring gear 2| being thereby axially moved to its idle position until the end of the pinion sleeve 24 engages the loosely-mounted, steel washer to abutting the hub member 3 of the barrel. During the demeshing operation as the pinion is moving to idle position, the frictionally mounted eccentric inertial mass 59 acquires substantially the same axial and rotational velocity of the pinion whereby the whole pinion assembly, inclusive of the inertial mass, has considerable axial and rotational kinetic energy due to its mass Velocity squared. When the pinion strikes the abut- 'ment or the steel washer 60, its axial motion is suddenly stopped, its rotation is decelerated and very abruptly assumes the speed of rotation of the armature shaft. The energy of the axial and rotary deceleration of the pinion is expended by the pinion attempting to rebound from the abutment or steel washer 60 toward the engine gear. The moment the axial movement of the pinion suddenly stops by striking the abutment, the axial movement of the inertial mass is decelerated but its rotation continues. Due to the large kinetic energy of rotation of the inertial mass, the same, by the cumulative effect of its frictional contact and radial load, imposes a frictional torque on the pinion opposing its attempt to rebound into the engine ring gear, and thereby screws the pinion back against the abutment, thus preventing the pinion from rebounding. This action cancels the rebound energy and both the pinion and inertial mass rotate with the armature shaft in a state of synchronization until the starting motor stops.

It should be observed that the possibility of sticking or binding of the coacting demeshing description of the present invention is intended to disclose an embodiment thereof to those skilled in the art, but that the invention is not to be construed as limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings,

since the invention is capable of being practiced and carried out in various ways without departing from the spirit of the invention. The language used in the specification relating to the operation and function of the elements of the invention is employed for purposes of description and not of limitation, and it is not intended to 1 limit the scope of the following claims beyond the requirements of the prior art.

What is claimed:

1. An engine starter drive including a power shaft, a barrel fixed to said shaft, a starter pinion mounted for longitudinal movement with respect to the power shaft and for rotary movement therewith to engage and crank a member of the engine to be started, driving torquetransmitting means between the pinion and barrel comprising loosely coupled screw threaded members splined respectively with the pinion and barrel and mounted in concentric relation with respect to the axis of rotation of the power I shaft, the threads on each of said members having non symmetrical threads mounted for movement on said shaft, a driving member having a driving connection with said sleeve for rotary and longitudinal movement to engage and to crank a member of the engine to be started, a barrel fixed to said shaft, a threaded nut member carried by said barrel having non-symmetrical threads for engagement with those of said sleeve, yielding means operatively interposed between said barrel and said nut member to yield under torque transmission from said shaft to the driving member, and a rotatable eccentric counterweight frictionally connected to said driving member to facilitate its axial movement into engagement with the engine member upon the initial rotation of said shaft.

3. In a starterfor engines, the combination of a power shaft, a piloting member rotatable by said shaft, a pinion mounted upon said shaft, a pair of loosely coupled threaded members forming a concentrically-mounted torque-transmitting connection, said threaded members splined respectively to said piloting member and pinion for moving the pinion longitudinally upon rotation of said shaft, arotatable eccentric weight mounted on said pinion, and spring means for frictionally connecting said eccentric weight to said pinion whereby upon the initial rotation of the shaft the longitudinal movement of the pinion is speeded up.

4. In a starter for engines including a power shaft, a pinion freel journaled thereon for longi- -tudinal movement into and out of mesh with an engine gear, a drive nut having a splined connection with a barrel member fixed to said shaft,

' a threaded member connected with said drive nut and having a limited lost motion connection with said pinion, a rotatable eccentric weight mounted on said pinion, and resilient means interposed 11 between said weight and threaded member performing the double function of urging the weight into engagement with the teeth of the pinion and holding the pinion and threaded member in extended relation.

5. In a starter for engines, the combination with means driven by a power shaft, a pinion ed connection to effect the engagement of the pinion with the engine member upon the initial rotation of the shaft.

6. In a starter for engines, the combination with a power shaft, a pinion mounted for longitudinal movement with respect to the power shaft and for rotary movement therewith to engage and crank a member of the engine to be started, a concentrically mounted loosely coupled connection formed of i-nterengaging inclined torquetransmitting splines having a reduced area of contacting engagement throughout their entire length interposed between said pinion and power shaft for moving said pinion longitudinally in and out of engagement with the engine member and maintaining an operative connection of the pinion with the engine member until the engine becomes self-operative, a rotatable member having its majormass arranged at one side of its axis of rotation mounted for longitudinal movement with the pinion and for rotation with respect thereto, and resilient means to cause frictional engagement between the rotatable member and the pinion.

'7. An engine starter drive including a power shaft, a member rigid with said shaft, a threaded nut piloted by said member in concentric relation to the axis of rotation of the shaft and formed with threads of non-symmetrical cross-section throughout their entire length, a shifting and control screw formed wi h threads of non-symmetrical cross-section throughout their length mounted on said shaft for threaded engagement with said nut, a starter pinion actuated by said control screw for engaging and cranking a member of the engine and be moved out of engagement when the engine starts, means carried by said member arranged for abutting engagement with the control screw when the starter pinion reaches a position for adequate engagement with the engine member, a rotatable eccentric weight mounted on the pinion for relative rotation with the starter pinion for synchronizing the pinion, spring means urging said rotatable eccentric weight into frictional engagement with the pinion, and resilient means operative to absorb the pinion meshing shock and yield upon the application of torque from the power shaft to the member of the engine to be started.

8. In a starter for engines, the combination with a power shaft, a pinion mounted on the shaft for engaging and cranking a member of the engine to be started, means for actuating said pinion from said power shaft including a nonsymmetrical loosely-coupled threaded torquetransmitting connection non-rotatably connected at each end to said pinion and shaft respectively, said connection being arranged to reduce the resistance to the longitudinal movement of the pinion toward the engine member upon the initial rotation of the shaft and for maintaining the pinion in operative engagement with the engine member until the engine is reliably self -operative, and a rotatable counter-weight frictionally mounted on the pinion for rotation with respect thereto.

9. In a starter for engines, the combination of a power shaft, a pinion mounted upon said shaft for engaging and cranking an engine gear, a driving torque-transmitting means between the power shaft and pinion including a pair of nonsym-metrical and loosely-coupled threaded members having splined connections with means carried by said shaft and pinion for moving the pinion into and out of engagement with the engine gear, a rotatable eccentric counter-weight journaled on said pinion, and a coil spring for urging said eccentric weight against the teeth of said pinion.

'10. An engine starter drive including a power shaft, a member fixed to said shaft, a sleeve having inclined splines on its bore piloted by said member in concentric relation with the axis of rotation of the power shaft, a shifting member mounted on said shaft having inclined splines loosely coupled to those of the sleeve to decrease friction therebetween providing a substantially uniform radial clearance and a generous spacing between their coacting sides, a starter pinion iournaled on said shaft having a splined connection with said shifting member and actuated by the action of the loosely-coupled splines for engaging and cranking a member of the engine to be started and causing its disengagement when the engine starts, a rotatable eccentric inertial mass frictionally' arranged on the pinion to provide relative rotary movement with said pinion. and means operative to yield upon application of torque b said pinion from the power shaft to the engine member.

11. In an engine starter dn've having a power shaft, rotatable means, a driven member mounted for longitudinal movement and rotary movement on said shaft, the combination with said rotatable means and driven member of a wrque-transmitting connection comprising two concentrically disposed members splined respectively to the driven member and power shaft rotatable means for moving the driven member longitudinally into engagement with a member of the engine to he started for transmitting torque from the power shaft to they engine, helical splines formed on each of said concentrically disposed members for interconnecting the .same, the splines being formed and correlated to provide a substantially uniform radialv clearance and a generous axial spacing thercbetween, the non-pressure side of said splines having an angle not greater than 15 degrees with planes perpendicular to the axis of rotation of the power shaft, and means to stop the longitudinal movement of the driven member for initiating the torque transmission.

12. An engine starter drive including a power shaft, a barrel rigid with said shaft to rotate in unison therewith, a threaded nut splined to said barrel in concentric relation with the axis of retation of the power shaft, 2. control screw journaled on said shaft and being coupled with said threaded nut providing a substantially uniform radial clearance to decrease their area of contacting engagement, a starter pinion journalcd on the shaft and having a reduced area of engagement therewith, a splined connection between said starter pinion and control screw providing positive rotary motion together and yielding longitudinal motion therebetween, means carried by the barrel adapted to be engaged by the control screw when the starter pinion reaches a position for adequate engagement with the engine memher, a rotatable eccentric weight frictionally coupled to the pinion for longitudinal movement therewith and for rotary movement with respect thereto, and means operative to yield under torque transmission from the power driven shaft to the starter pinion.

13. An engine starter drive including a rotatable power shaft, a barrel fixed to said shaft, a sleeve splined to said barrel and having on its interior helical splines, a control member mounted on said shaft and having helical splines coupled to those of the sleeve forming a torque-transmitting connection, the pressure side of the coacting splines of said torque-transmitting connection formed at an angle ranging between 30 to 50 degrees with planes perpendicular to the axis of rotation, the non-pressure side of said splines having an angle not greater than 15 degrees with planes perpendicular to the axis of rotation, a starter pinion freely journaled on said shaft having a splined connection with said control member for rotary motion together and limited movement axially thereof and adapted to be actuated thereby for engaging and cranking a member of the engine to be started, means carried by the barrel for stopping the longitudinal movement on the pinion, and spring means operatively interposed between said sleeve and barrel to yield upon engagement of said pinion with the engine member.

14. In a starter for engines having means rotatable by a power shaft and a pinion mounted on the shaft for longitudinal movement with respect thereto and for rotary movement therewith to engage and crank a member of the engine to be started, the combination with said means and pinion of driving torque-transmitting means comprising two interengaging members each having threads of about 30 angle on the driving side and of about angle on the demeshing side, each of said interengaging members having a splined connection with pinion and said means rotatable by the power shaft for rotary movement therewith and limited movement axially thereof, an eccentric inertial mass adapted to be moved longitudinally with said pinion and frictionally coupled to the pinion for rotation with respect to said pinion, and a helical spring operatively interposed between said power shaft rotatable means and threaded member splined thereto to yield under torque transmission from the power driven shaft to the starter pinion.

15. An engine starter drive including a power shaft, a barrel rigid with said shaft for rotation therewith, a sleeve carried by said barrel having inclined splines, a shifting member mounted on the power shaft having inclined splines coupled to those of the sleeve, a starter pinion freely journaled on the power shaft for engaging and cranking a member of the engine to be started, a splined connection between said starter pinion and shifting member providing positive rotary motion together and longitudinal lost motion therebetween, an eccentric inertial mass mounted for rotation with respect to said pinion, and resilient means urging said inertial mass into engagement with the teeth of said pinion whereby said mass moves longitudinally with said pinion.

1-6. In a starter for engines, the combination with a power shaft, a pinion having a sleeve and being freely journaled on the power shaft for longitudinal movement into and out of mesh with an engine gear, a drive nut having non-symmetrical threads carried by a member fixed to the power shaft, a screw member provided with non-symmetrical threads engaging those of the drive nut, a limited longitudinal lost motion connection between said screw and the sleeve of said pinion, a rotatable eccentric counterweight journaled on the sleeve of said pinion, and a coil spring surrounding said sleeve interposed between said counterweight and said screw performing the double function of urging said counterweight against the teeth of the pinion and opposing movement of said pinion toward said screw.

17. In an engine starter for engines, the combination with a power shaft, a starter pinion mounted for longitudinal movement with respect to the power shaft and for rotary movement therewith to engage and crank a member of the engine to be started, a loosely coupled screw threaded torque transmitting connection interposed between said pinion and shaft, means carried by said power shaft for piloting and driving said connection in concentric relation with the axis of rotation of the shaft, said loosely coupled torque transmitting connection comprising threads of non-symmetrical cross-section formed and arranged to provide liberal axial spacing between their coacting sides as well as liberal uniform radial clearance between their respective major and minor diameters of the coacting threads to reduce their area of threaded engagement and thereby decrease the frictional resistance for relative movement therebetween, and the pressure side of the coacting threads of said torque transmitting connection being inclined throughout their length at a greater angle from the vertical than the non-pressure side.

18. An engine starter drive including a power shaft, means rigid with said shaft to rotate therewith, a pinion on said shaft mounted for rotation and longitudinal movement into and out of mesh of an engine gear, provisions on said pinion for reducing the area of contacting engagement with said shaft and thereby decrease frictional resistance to their relative movement, a drive nut having a piloting driving connection with said shaft operated means for rotation in concentric relation to the axis of rotation of said shaft, a control screw journaled on said shaft having spaced sections of limited area to reduce its engagement with the shaft and thereby decrease frictional resistance to their relative movement, said control screw having a loosely coupled concentric threaded engagement With said nut providing a substantially uniform radial space between their coacting threads to reduce their area of threaded engagement and thereby decrease frictional resistance to their relative movement, saidstarter pinion and control screw having a connection for positive rotary motion together.

GEORGE W.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,809,017 Brownlee June 9, 1931 2,084,813 Lansing June 22, 1937 

